This invention relates to a detector conveniently usable for detecting the user's hand as it approaches the door handle of an automobile and generating a trigger signal for initiating the automatic unlocking operation of a passive entry system for the automobile. The invention also relates to lock controllers using such a detector.
In recent years, proposals are being made for vehicle entry system apparatus for automatically operating an equipment on a vehicle by carrying out two-way communications between a device carried by the user and a vehicle-mounted main device and thereby carrying out a required comparison, and some of such apparatus are actually coming to be used. With such an apparatus adapted to carry out two-way communications, an answer signal containing a necessary code can be automatically transmitted from the device carried by the user to the main device in response to a request signal (such as a startup signal for starting up the device being carried) transmitted from the main device and hence an equipment on a vehicle can be caused to carry out a specified operation without the user carrying out any operations at all. With a vehicle entry system, for example, the user carrying a portable device may have only to approach the door of a specified vehicle to which a corresponding main device is mounted for establishing a two-way communication between them such that a lock-opening command is automatically outputted to the locked door and the locked door becomes automatically unlocked. Such highly convenient entry systems capable of locking and unlocking a vehicle door basically without requiring any conscious effort on the part of the user are sometimes referred to as a passive entry system (or a smart entry system) as an improved version of general keyless entry systems, and needs for such systems are becoming higher as they are capable of increasing the market values of the vehicles.
If it is attempted with such a passive entry system to save the power of the vehicle battery by transmitting request signals from the main device only when they are necessary, it may become necessary to provide a detector for detecting the user approaching or contacting the vehicle (such as to its door handle). Optical sensors and capacitance sensors have recently been used for such a purpose. Another approach has been to provide a push-button switch on or near the door handle for the user to operate on for generating a trigger signal for an automatic locking operation when the user leaves the vehicle.
Optical sensors are adapted, for example, to detect the user's hand approaching the door handle on the basis of a change in the output from a light-receiving element as light outputted from a light-emitting element is screened or reflected by the user's hand. Capacitance sensors are so-called touch sensors and adapted, as disclosed in Japanese Patent Publication Tokkai 2002-295064, to detect the user's hand approaching the door handle based on a change in the capacitance of a capacitor within the sensor by the contact of the user's hand. Examples of known non-contact type of short-distance sensors include impulse radars which are adapted to make detections by analyzing reflected waves by using a microcomputer and are used, for example, for the detection of land mines, as disclosed in International Patent Publication 00/023,762.
Prior art technologies characterized as using a detector or a switch as explained above have the following problems.
(A) Optical sensors may function incorrectly in the presence of unwanted objects such as rain drops and dead leaves.
(B) Response characteristics of optical sensors and capacitance sensors are not sufficient because their detection areas are small (or their detection distance is short) and the system depending on such a sensor may function incorrectly. If such a sensor is set to the door handle of a vehicle for providing a trigger for the transmission of a request signal in a passive entry system of the vehicle, for example, the user's hand may not be detected and hence the request signal may not be outputted until the hand nearly touches the sensor. Thus, the user may have already started to pull the handle in order to open the door but the door may not be unlocked yet. In other words, the user may try to open the locked door by using a passive entry system but its automatic unlocking operation may be delayed and the door may refuse to open immediately.
(C) Since sensor elements which are relatively large and hence are difficult to be contained must be provided to a component such as a door handle intended to detect the approaching target object of detection, the shape and the size of such a component may have to be modified significantly and hence the freedom in its design is severely restricted.
(D) When a trigger of the aforementioned kind, for example, for a passive entry system of a vehicle is generated by means of a switch to be operated by the user, the freedom of design for the part to which the switch is to be attached, such as the door or the door handle, is significantly limited. Besides, a switch operation by the user is required. It is inconvenient and affects the operability adversely.
Sensors of electromagnetic wave types such as aforementioned impulse radars are examples of non-contact type sensors capable of setting the detection area to be large and not influenced by dirt. The present inventors attempted to use such sensors of electromagnetic wave type as the aforementioned detectors but the following problems still remained.
(E) It is difficult to normalize the detection area. If the detection area is made larger in view of Problem (B) above, a trigger may be generated against the user's intention, for example, when the user happens to lean on the door handle. Erroneous operations are also likely due to a strong external noise such as electromagnetic waves from a portable telephone.
(F) Only a detection area of a fixed size could be set for a prior art sensor of electromagnetic wave type and hence it was impossible to adjust the detection area optimally according to the condition of the system to which it is to be used. As a trigger for automatic unlocking by a passive entry system, for example, it is necessary to be able to detect the use's hand at an early stage within a relatively large detection area in view of the aforementioned Problem (B). As a trigger for automatic locking by the same system, however, there is no such problem (Problem (B)) and hence it is desirable to detect the approaching user's hand reliably within a relatively small area without committing an erroneous operation. If the detection area of only a fixed size can be set, however, this kind of adaptable operations cannot be carried out and a switch as explained above may be required to be set for the generation of a trigger for automatic locking and hence aforementioned Problem (D) remains.
It may be considered to simply use a plurality of sensors of electromagnetic wave type for setting up a plurality of detection areas. This, however, means that a plurality of sets of antennas for transmission and reception must be set up near the door handle or in its neighborhood and this results in a complicated structure. This means that aforementioned Problem (C) cannot be eliminated satisfactorily. There is also the disadvantage that the amount of power consumed by the detector increases by a factor of 2, 3, etc.
It is therefore an object of this invention to make use of the technology of electromagnetic radars to provide an improved detector superior in operational reliability, response characteristics, operability by the user and capability of being mounted to a vehicle as well as from the points of view of size, freedom in design and power consumption.
It is another object of the invention to provide a lock controller using such a detector.